For a wireless data network operator to operate two or more wireless protocols such as a DataTAC.RTM. network and a ReFLEX.TM. 25 network employing today's technology would require two distinct networks, operating in parallel. They would not be able to share channels or equipment efficiently.
A minor variation, would allow the sharing of the base station links (a significant cost item) by adding multiplexers and demultiplexers at each end of the links. This has however never been done and there may be difficulties of which we are unaware, such as timing effects (additional latency variation) caused by the shared links.
Another technique that could be used would allow the two dissimilar systems to simply "aloha" on top of each other. This means that each network would ignore the other, but share the radio channels and receivers. The receivers would be capable of receiving and demodulating either of the dissimilar protocols. There would be many collisions with this mechanism, and they would significantly impair the capacity of the reverse channels of both systems. Also, this technique would require the DataTAC system to operate in single frequency mode, which is not the normal mode of operation for DataTAC 5000 networks. In any case, the method claimed herein is significantly different and avoids the detriments described above.
A similar but different prior technology for sharing channels occurs in (cellular digital packet data) CDPD networks, when the CDPD channels are shared with AMPS voice channels. The technique used in this case involves "channel hopping", which basically requires the CDPD channel to move to a different frequency when the CDPD base station detects voice activity on the shared channel. This is also a completely different (and less effective) technique than will be described with the present invention.